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Chapter 3
Copula-VAR Analysis of the Relation between GDP,
Imports, Exports: ASEAN Case
Warattaya Chinnakum1 and Songsak Sriboonchitta 2
1 Faculty of Economics ,Chiang Mai University
E-mail: [email protected]
2 Faculty of Economics ,Chiang Mai University
E-mail: [email protected]
This study concentrates on the causal relationship among output, imports, and
exports in ASEAN economies for the period 1980–2010. The investigation is
conducted in a time series framework using a vector autoregressive model with
copula approach, and impulse response function to test the trade variables of
exports and imports for exogenous or endogenous induced growth. Moreover,
results suggest there is no causal relation among imports, exports, and output in
Malaysia, Thailand, and Brunei. In contrast, the study found empirical evidence
in support of bi-directional causal relationship between exports and GDP growth
for Laos and The Philippines. Furthermore, the results of Indonesia, Singapore,
and Vietnam support only ELG hypothesis, not GLE hypothesis. Empirical
results also suggest that there is evidence in support of ILG hypothesis for The
Philippines, Indonesia, Singapore, and Vietnam. Thus, it is reasonable to
conclude that for several ASEAN countries, both exports and imports play a very
important role in stimulating economic growth.
34 Chapter 3 W. Chinnakum and S. Sriboonchitta
1. Introduction
International trade is often considered to be a main determinant of economic
growth in several countries, especially the Association of Southeast Asian Nations, or
ASEAN, countries, for which their growth rate of exports and imports have been grown
faster and higher than their GDP growth during the past thirty years. Table 1 shows
evidence that export growth and import growth are more than GDP growth from 1990 to
2010 in the ASEAN countries (except Vietnam, Laos, Thailand, and Cambodia in
1990), which implies that exports and imports could be main factors to determine output
in the ASEAN economies. Table 1 also shows the trend of export growth and import
growth. Export growth in ASEAN has continually increased since 1990 in most
countries, which arises from export-oriented market-based policies and free trade area
agreements. Moreover, import growths also increased from 1990 to 2010, and were
mainly due to imports of raw materials, capital goods, and machinery to produce for
domestic and exports sector. Furthermore, in 2015, ASEAN aims to integrate ten
countries to be one regional economic community called the ASEAN Economic
Community (AEC), and AEC considers the following key characteristics: (a) a single
market and production base, (b) a highly competitive economic region, (c) a region of
equitable economic development, and (d) a region fully integrated into the global
economy (ASEAN (2012)). This mean the economic integration will encourage trade in
the ASEAN countries and could be lead to increases in GDP in the future.
Therefore, the primary purpose of this study is to investigate the relationship
between trade and economic growth in the ASEAN countries which is important for
policymakers and governments in the ASEAN countries to decide direction or
appropriate policy for trade in their countries, and to decide whether the policies should
be the same or different in each country after economic integration.
Moreover, in recent years, many research projects have studied the relationship
between trade and economic growth, and a large volume of empirical research has
confirmed that trade is crucial and necessary for growth and development (Kababie
(2010)). However, most studies are interested only in exports factor and attempt to test
two hypotheses, which are Exports Lead Growth and Growth Lead Exports, but ignore
the imports factor. Reizman, Summers, and Whiteman (1996) argued that exports are
not only one factor to determine growth, but imports are also important, and the result
will be incomplete and spurious if analyzing a system without including imports. In
addition, Awokuse (2008) states that exports in some countries are not an important
engine or condition to drive the economy, and Kababie (2010) has established that
imports are valuable to economic growth for three primary reasons: (1) they are a source
of technology transfers; (2) they promote innovation through imports competition; and
(3) they provide factors of production, which are used in both domestic and export
sectors.
Asian Economic Reconstruction and Development under New Challenges 35
TABLE 1. GDP growth, Exports growth, and Imports growth of 10 ASEAN countries
from 1990-2010.
Country 1990 2000 2010
GDP
growth
Exports
growth
Imports
growth
GDP
growth
Exports
growth
Imports
growth
GDP
growth
Exports
growth
Imports
growth
Brunei 20.95 17.51 16.50 0.54 23.90 7.49 17.26 28.06 22.86
Vietnam 2.84 2.12 -6.27 8.62 25.49 33.16 11.17 22.07 19.18
Malaysia 13.34 17.44 29.15 16.73 16.09 25.50 23.25 26.45 33.13
Indonesia 12.79 17.07 33.61 17.87 27.67 39.63 31.49 35.43 39.93
The
Philippines 3.82 5.69 16.33 -2.38 7.70 12.12 18.46 30.64 19.27
Singapore 23.66 17.96 22.67 11.11 20.37 21.21 22.49 30.50 26.37
Thailand 18.53 14.28 31.69 0.08 17.90 22.99 20.93 28.55 36.91
Lao PDR 19.30 -32.44 15.43 15.33 -15.40 -14.72 15.42 44.37 23.61
Cambodia 159.83 101.25 8.00 4.13 7.95 14.61 8.08 11.84 25.55
Myanmar N/A N/A N/A 4.93 42.13 20.26 28.83 9.96 40.60
Source: IMF (2012)
Note: N/A = data are not available
Therefore, this study investigates the causal relationship among exports, imports,
and economic growth for the ASEAN economies within an integrated concept that
investigates the role of both exports and imports. The contributions of this paper are the
following: 1) export growth and import growth are included in the model as endogenous
variables which previous empirical studies specify as exogenous variables. 2) We
employ copula-VAR model (suggested by Bianchi, et. al (2010)). The advantage of
copula approach is to build flexible multivariate distributions and to consist in
representing the joint probability distribution by separating the impact of the marginals
from the association structure, explained by the copula functional form. Moreover, there
are no empirical studies using copula-VAR model to investigate causality among
exports, imports, and GDP.
The rest of this article is organized as follows: Section 2 provides a brief
empirical overview of the exports, imports, and output growth relationship. Section 3
discusses the analytical framework and some methodological issues. Section 4 presents
empirical findings, and Section 5 contains the concluding remarks.
2. Literature review
The role of exports and imports in promoting growth is perhaps the most
discussed topic as far as the role of trade in the economy is concerned. Although there
are vast empirical studies that emphasize the positive relationship between trade and
economics, Rodriguez and Rodrik (1999) highlight that the controversy between the
relationship of trade and economic growth has yet to be resolved. They mention the
problem of endogenous relations between income and trade. For example, recent studies
have observed that countries with high incomes tends to trade more, and when the trade
36 Chapter 3 W. Chinnakum and S. Sriboonchitta
(especially exports) rises, the income also increases. Therefore, to consider only one
direction from trade to economic growth will lead to incomplete results.
According to Awokuse (2008), there are three dominant hypotheses proposed to
the economic literature: 1) Export-Led Growth (ELG), 2) Growth-Led Export (GLE),
and 3) Imports-Led Growth (ILG). Of the three hypotheses, most empirical testing has
been carried out on the ELG and GLE. However, the empirical evidence on the
relationship among exports growth, imports growth, and GDP growth is rather mixed,
and the results of different regions or countries in different periods of time provide
different conclusions.
Several pieces of empirical evidence on the ELG hypothesis have shown that
there is a link between economic growth and export growth. But debates still surround
the direction of causality. While some researchers have found evidence in support of the
ELG hypothesis (Ramos (2001), Sato and Fukushige (2011)), others (Reppas and
Christopoulos (2005)) either found reverse causal flow from economic growth to
exports growth, or support the alternative GLE hypothesis. Moreover, in some cases, the
empirical evidence indicated a bi-directional causal relationship (Khan, et al. (1995),
Zang and Balmbridge (2012)).
Moreover, on the context of ILG, endogenous growth models show that imports
can be a channel for long-run economic growth because it provides domestic firms with
access to needed intermediate factors and foreign technology (Coe and Helpman, 1995).
Thangavelu and Rajaguru (2004) found that there is no export-led productivity growth
for Hong Kong, Indonesia, Japan, Taiwan, or Thailand. However, significant causal
effects were found from imports to productivity growth in India, Indonesia, Malaysia,
The Philippines, Singapore, and Taiwan, which similarly result as Marwah and Tavakoli
(2004) who consider the effect of foreign direct investment (FDI) and imports on
economic growth in four Asian countries (Indonesia, Malaysia, The Philippines, and
Thailand) and the result shows FDI and imports are important factors to determine
economic growth. In Awokuse (2008), they suggest that economic growth could be
driven primarily by growth in imports, and Çetinkaya and Erdoğan (2010) also found
imports influenced GDP in Turkey. Pistoresi and Rinaldi (2012) found exports were not
the only or the main driver of economic growth in Italy from1863 to 2004.
3. Methodology
This article attempts to capture the causality among exports, imports and GDP
via the vector autoregressive (VAR) framework of Sims (1980). Moreover, traditional
approach assumed the joint distribution of error term is normality. However, Bianchi
et.al (2010) proposes to use of copula to construct the joint distribution and their result
show that the copula-Vector Autoregression (VAR) model outperforms or at worst
compares similarly to normal VAR models, keeping the same computational tractability
of the latter approach. Therefore, in our paper, we employ copula approach to construct
VAR model and compare with normal VAR model. This section provides a brief
discussion of the copula-VAR model adopted in this study. Since the vector
Asian Economic Reconstruction and Development under New Challenges 37
autoregressive (VAR) is fairly commonplace and well-document elsewhere, only a brief
overview is provided here.
Let ),...,,( 21 ntttt yyyY denote an )1( n vector of n endogenous variables. The
general p-lag vector autoregressive ))(( pVAR model has the form
TthYYYcY tptpttt ,...,1,...2211 (1)
where i are )( nn coefficient matrices and t is standard innovation which
has an )1( n unobservable zero mean and variance one.
Moreover, their conditional joint distribution is );,...,( ,,1 tnttH with the
correlation parameters vector . From the Sklar Theorem (1959), the joint distribution
can be written in the copula as
:):(),...,:();,...,( ,1,11,,1 ntnnttntt FFCH (2)
where ):( , itiiF is marginal distribution functions of ti , with marginal
parameter i and :C is the copula function which copula parameter . A copula is a
function that links together univariate distribution functions to form a multivariate
distribution function. Joe (1997) and Nelsen (2006) provide a complete monograph of
an introduction to the theory of copulas and a large selection of related models. Another
reviews such as Frees and Valdez (1998) and Cherubini et al. (2004) provide more
detail about the application in actuarial and financial settings.
From (2) the expression of the corresponding densities can be derived. By taking
derivatives to equation (2) we have:
),...,( 1 nf =
n
n
n H
1
1 ,, =
n
nn
n FFC
1
11 ,,
=
n
i i
ii
nn
nn
n
d
dF
FF
FFC
111
11 ,,
=
n
i
iinn fFFc1
11 ,, (3)
From inverse Sklar’s theorem which provide
nuuC ,,1 = nn uFuFF 1
1
1
1 ,, (4)
where niuFFu iiiiii ,...,2,1,1 .
Therefore, equation (4) becomes:
38 Chapter 3 W. Chinnakum and S. Sriboonchitta
nuuc ,,1 =
n
i
iii
nn
uFf
uFuFf
1
1
1
1
1
1 ,, (5)
where nuuc ,,1 is the multivariate copula density.
By using equation (5), we can derive the Normal-copula, whose probability
distribution and density function is:
n
G uuC ,,1 =
:,, 1
1
1
nuu (6)
and
n
G uuc ,,1 =
n
i
ii
n
u
uu
1
1
1
1
1 ,,
(7)
where 1 is the univariate Gaussian inverse distribution function
( iiiu ,while is the correlation matrix.
Moreover, there are alternative copula families which are called Archimedean
copulas (such as Clayton's copula ,Rotated Clayton copula, Plackett copula, Frank
copula, Gumbel copula, Rotated Gumbel copula and Symmetries Joe-Clayton copula)
are provided to model the joint distribution. However, these copulas can become
inflexible in high-dimensions and do not allow for different dependency structure
between pairs of variables.
Moreover, Aas et.al(2009) presented a method to build high dimension copulas
using pair-copulas as building blocks and they show that the pair-copula decomposition
treated in their studies are more flexible to build higher dimension copula. This
decompositions are called vine copulas. Initially proposed by Joe (1996) and developed
in more detail in Bedford and Cooke (2001, 2002) ,Kurowicka and Cooke(2006) and
Brechmann ans Schepsmeirer (2011), vines are a flexible graphical model for describing
multivariate copulas built up using a cascade of bivariate copulas, so-called pair-
copulas. According to Aas, et.al(2009) ,they described statistical inference techniques
for the two classes of canonical (C-) and D-vines. Moreover, in this study, we provide
C-vines copula in 3-dimensions and the tree of C-vine show as Figure 1
Asian Economic Reconstruction and Development under New Challenges 39
T1
T2
Figure 1. A canonical vine with 3 variables ,2 trees and 3 edges.
The general expression for the canonical structure in the 3-dimensions case is
),,( 321 f = 32232112321 ,,)()()( FFcFFcfff
1312123, FFc (8)
or in the n-dimensions case we can write the general expression as follow:
n
i
n
i
in
j
ijiiijiiiijiiii FFcff1
1
1 1
)1(:1,1111)1(:1,,,(),,,()()(
(9)
where nif i ,...,1, denote the marginal densities and )1(:1, ijii
c bivariate copula
densities with parameter(s) )1(:1, ijii
.
The crucial question for inference is how to obtain the conditional distribution
functions F for an m-dimensional vector . For a pair-copula term in tree m+1,
this can easily be established using the pair-copulas by sequentially applying the
relationship
jj
jjjv
F
FFCFh
jj
,
, (10)
where j is an arbitrary component of and j denotes the ( 1m )-
dimensional vector excluding j (Joe 1996). Further jj v
C
is a bivariate copula
23/1
13
12
1
2
3
12 13
40 Chapter 3 W. Chinnakum and S. Sriboonchitta
distribution function with parameter(s) specified in tree m . The notation of the h -
function is introduced for convenience (cp. Aas et al. 2009).
Copula and marginal estimation
The estimate the mariginal and copula parameter, Bianchi (2010) provided
multi-step procedure is known as the method of Inference Functions for Margins (IFM).
According to the IFM method, the parameters of marginal distributions are estimated
separately from the parameters of the copula. The estimation following two steps:
(1) Estimate the parameters nii ,...,1, of the marginal distributions iF using
the Maximum Likelihood (ML) method:
);(logmaxarg)(maxargˆ1
,
T
t
itiii
i
i fl (11)
where il is the log-likelihood function of the marginal distribution iF ;
(2) Estimate the copula parameters , given the estimations performed in Step
1:
T
t
ntnnt
c FFcl1
,1,11 ;ˆ;,...,ˆ;logmaxarg)(maxargˆ (12)
where cl is the log-likelihood function of the copula.
4. Empirical Analysis and Results
4.1 Data and unit root properties
Data was obtained for eight ASEAN countries1: Brunei, Vietnam, Malaysia,
Indonesia, Philippines, Singapore, Thailand and Laos. The data set consists of
observations for GDP growth (GDP), exports growth (EXPORT), imports growth
(IMPORT). Our estimates are based on annual data for the sample period 1980-2010.
Data are drawn from two main sources: (a) the International Monetary Fund (IMF,
various issues) and the World Development Indicator (World Bank, various issues).
1 We cut Cambodia and Myanmar out of sample data because data are unavailable.
Asian Economic Reconstruction and Development under New Challenges 41
TABLE 2. Trends in GDP growth, exports and imports from 1990 to 2010
Country GDP Growth (%) Exports (% of GDP) Imports (% of GDP)
1990 2000 2010 1990 2000 2010 1990 2000 2010
Brunei 20.95 0.54 17.26 59.14 73.51 63.12 26.74 33.19 23.96
Vietnam 2.84 8.62 11.17 39.01 46.46 67.41 43.91 50.16 80.49
Malaysia 13.34 16.73 23.25 66.83 104.66 83.66 66.27 87.66 69.33
Indonesia 12.79 17.87 31.49 22.58 37.66 22.28 19.34 20.31 19.16
Philippines 3.82 -2.38 18.46 16.74 47.18 25.87 26.54 42.57 27.42
Singapore 23.66 11.11 22.49 136.10 146.50 155.53 156.98 142.76 136.72
Thailand 18.53 0.08 20.93 26.94 56.19 61.26 39.03 50.46 57.89
Laos 19.30 15.33 15.42 7.04 23.86 33.99 16.24 42.06 55.34
Source: IMF and World Bank
The trends in GDP growth, share of exports to GDP and share of imports of
GDP are shown in Table 2. Across ASEAN countries, the trends in GDP growth do not
show any similarly trends. GDP growth in Brunei, Philippines, Singapore, Thailand and
Laos decrease from 1990 to 2000 and increase from 2000 to 2010 while GDP growth in
Vietnam, Malaysia and Indonesia continuously increase from 1990 to 2010. The data
clearly show the highly share of exports and imports on these countries GDP. Compare
to GDP growth, there are upward trend for exports and imports from 1990 to 2010
across all the ASEAN countries under study.
Before estimate the VAR model, we have to check whether each time series
variable is stationary in levels or stationary after first differencing. Two univariate unit
root tests (the augmented Dickey–Fuller (ADF) and Phillips–Perron (PP)) were
examined for each of the variables and were shown in Table 3.
TABLE 3. Tests for unit root
ADF PP Jarque-Bera Prob Skewness Kurtosis
Brunei
GDP -4.811*** -4.811*** 2.345 0.310 0.148 4.572
Exports -6.647*** -6.647*** 0.377 0.828 0.812 3.588
Imports -4.338*** -4.338*** 106.020*** 0.000 -0.787 4.662
Vietnam
GDP -5.088*** -6.330*** 6.608** 0.037 0.105 5.290
Exports -5.505*** -11.965*** 122.658*** 0.000 2.849 11.104
Imports -4.781*** -7.386*** 463.091*** 0.000 4.010 20.497
Indonesia
GDP -6.014*** -6.242*** 47.954*** 0.000 -1.491 8.428
Exports -5.143*** -5.146*** 0.648 0.723 -0.338 2.752
Imports -5.280*** -5.295*** 0.749 0.688 0.320 3.436
Malaysia
GDP -4.707*** -4.652*** 3.227 0.199 -0.795 2.767
Exports -4.977*** -4.989*** 1.076 0.584 -0.421 2.609
Imports -3.898** -3.774** 17.529*** 0.000 -1.524 5.176
42 Chapter 3 W. Chinnakum and S. Sriboonchitta
ADF PP Jarque-Bera Prob Skewness Kurtosis
Philippines
GDP -4.342*** -4.346*** 1.828 0.401 -0.603 2.915
Exports -3.636** -3.611** 1.034 0.596 -0.439 2.760
Imports -3.700** -3.684** 1.332 0.514 -0.483 2.636
Singapore
GDP -3.241** -3.289** 2.806 0.246 -0.745 2.846
Exports -4.234** -4.116** 0.464 0.793 -0.240 2.626
Imports -4.520*** -4.515*** 2.279 0.320 -0.674 2.932
Thailand
GDP -3.190** -3.251** 14.856*** 0.001 -1.444 4.883
Exports -3.999*** -3.886** 1.220 0.543 -0.214 2.110
Imports -4.173*** -3.913** 0.121 0.941 -0.104 2.767
Loas
GDP -3.959*** -3.758** 3.200 0.202 0.148 4.572
Exports -5.017*** -7.741*** 3.730 0.155 0.812 3.588
Imports -5.365*** -5.286*** 6.547** 0.038 -0.787 4.662
Source: Computation
Notes: ** and *** denotes rejection of the null hypothesis of unit roots for the ADF tests and PP tests at
the 5% and 10% significance levels.
** and *** denotes rejection of the null hypothesis of normality for the Jarque-Bera tests at the 5% and
10% significance levels.
The combination of the unit root tests results (see Table 3) suggest that the GDP
growth, imports growth and exports growth are integrated of order zero (i.e., I(0)) or
stationary at level and so we can construct VAR model without take the differentiate.
Table 3 also provides the normality test for all of variables and the Jarque-Bera on some
of variables reject normality implied that not all marginal of the variables are normal
distribution. Therefore, we can not assume the joint distribution of them is multivariate
normality.
4.2 Estimation of copula-VAR model
The next step is to formulate the appropriate VAR model. The variables in the
VAR models are used on their stationary level. The initial task in estimating the VAR
model is to determine the optimum order of lag length. Moreover, in the real world
economy, GDP, exports and imports always will delay for recognized the external and
internal impact including the impact of changing in value of GDP, exports and imports
on other side of economy were not immediately exist. In order to select the lag length
of VAR model, sequential modified LR test statistic (LR), Akaike information criterion
(AIC), Schwarz information criterion (SIC) and Hannan-Quinn information criterion
(HQ) are used. Table 4 presents selected lag length of each country VAR model.
Asian Economic Reconstruction and Development under New Challenges 43
TABLE 4 Selected Lag Lengths
Country selected lag lengths
Brunei 0
Indonesia 2
Laos 1
Malaysia 0
Philippines 6
Singapore 6
Thailand 0
Vietnam 6
Source: Computation
Table 4 shows that there is no causality among exports, imports and GDP in
three countries (Brunei, Malaysia and Thailand). In the case of Laos, there is 1 lag
length while 2 lag lengths exist in Indonesia. In addition, the proper lag order for
Philippines, Singapore and Vietnam are 6.
After chose the appropriate lag length for each country, we estimate the
parameters in VAR model and copula parameter and results of each country are
separately presented.
1) Long-run relationship among exports, imports and GDP via copula-VAR model
for Indonesia
Table 5 shows that imports and exports are important factors to determined
economic growth in Indonesia at 5 percent significant level or better. The coefficient of
EXPORT(t-1) on GDP growth shows that increase in 1 percent of exports growth will
lead GDP growth increase 0.301 percent. Moreover, the coefficient of IMPORT(t-1) on
GDP growth is 0.758 means the 1 percent increase of imports growth will increase GDP
growth 0.758 percent. This result indicates the impact of imports on GDP is larger than
impact of exports on GDP in the case of Indonesia.
Furthermore, there is relationship between exports growth and imports growth
and Table 5 shows that exports led imports in Indonesia (at 10 percent significant level)
but there is no causal relationship from imports to exports and there is also no causality
from GDP to imports or exports. This result implies that imports and exports policy can
encourage growth in Indonesia and imports are relatively more important than exports
to GDP growth. We can write the relation in the functional form as follow:
GDP growth = f(EXPORT(t-1), IMPORT(t-1))
Imports growth = f (EXPORT(t-2))
Since the joint copula model requires the correct specification of the marginal
models and their probability transforms will be iid uniform(0,1), so we provide the KS
Test for if the probability transforms are uniform(0,1) and Box-Ljung Test for
44 Chapter 3 W. Chinnakum and S. Sriboonchitta
Autocorrelation. The null hypothesis of KS Test is variable has uniform distribution
and the result from Table 6 rejects the null hypothesis for all 3 margins which implied
that GDP growth, exports growth and imports growth have uniform distribution in the
case of Indonesia. The Ljung–Box tests on the standardized residuals in levels reported
in Table 6 highlight no autocorrelation. These results provide significant evidence that
our marginal models are correctly specified.
TABLE 5 Causality relationship between Exports, imports and GDP in Indonesia
Variables EXPORT IMPORT GDP
Coefficient t-stat Coefficient t-stat Coefficient t-stat
Constant 5.085* 1.919 7.208 1.563 7.785** 2.111
EXPORT(t-1) 0.036 0.138 -0.103 -0.706 0.301** 2.012
IMPORT(t-1) -0.451 -0.996 -0.117 -0.463 0.758*** 2.915
GDP(t-1) 0.242 0.668 -0.082 -0.406 -0.104 -0.499
EXPORT(t-2) -0.104 -0.378 0.247* 1.840 -0.130 -0.774
IMPORT(t-2) 0.378 0.788 -0.177 -0.755 0.154 0.527
GDP(t-2) 0.273 0.712 0.184 0.983 -0.329 -1.405
Log-Likelihood -351.280
AIC 756.559
BIC 794.392
Source: Computation
Notes: *,** and *** denote 10%, 5% and 1% levels of significance respectively.
TABLE 6 testing the assumptions of i.i.d and Test for Autocorrelation
KS test for uniform distribution
Null Hypothesis: Variable has uniform distribution
statistic pValue Hypothesis
Margins of GDP growth 0.0936 0.9448 0 (acceptance)
Margins of exports growth 0.0827 0.9823 0 (acceptance)
Margins of imports growth 0.1351 0.6124 0 (acceptance)
Box-Ljung Test for Autocorrelation
Null Hypothesis: No autocorrelation
Q-Stat pValue Hypothesis
Margins of GDP growth 5.9429 0.9990 0 (acceptance)
Margins of exports growth 9.0467 0.9824 0 (acceptance)
Margins of imports growth 10.9125 0.9485 0 (acceptance)
Source: computation
Next, we estimate the copula parameter and we consider pairwise dependence,
so we model bivariate distributions of returns for computational tractability. To each
pair of variables, we fit the following copulas: Normal copula, Clayton's copula,
Rotated Clayton copula, Placket copula, Frank copula, Gumbel copula,and Rotated
Gumbel copula . We fit the copulas to the pairs of standardized residuals, obtained after
fitting VAR models to each returns series, transformed to uniform distribution by their
Asian Economic Reconstruction and Development under New Challenges 45
empirical distribution functions. The copula selection is done on the basis of AIC and
BIC perspective. Table 7 shows the optimal copulas and their estimated parameters.
TABLE 7 Copula correlation matrix
Family Copula
parameter
Kendall’s
tau
GDP and Export Frank 4.817 0.45
GDP and Import rotated Gumbel copula (180 degrees;
“survival Gumbel”) 1.676 0.4
Export and Import condition on GDP Frank 8.002 0.6
Source: Computation
Table 7 shows that, in the case of GDP-export pair and Export-Import pair, the
Frank copula are the most appropriate to model the dependence structure. In the case of
GDP-Import pair is given to the rotated Gumbel copula. The Kendall’s tau shows the
positive dependence of each pair.
2) Long-run relationship among exports, imports and GDP via copula-VAR model
for Laos
The result of Table 8 indicates that lag of exports and GDP are important factors
to determined GDP growth in Laos. In addition, there is bidirectional relation between
exports and GDP which support ELG and GLE hypotheses. The result also shows that
exports led imports in Laos. However, all coefficients of imports are insignificant which
can imply unimportant of imports policy. We can write this relation in the functional
form as follow:
GDP growth = f(EXPORT(t-1), GDP(t-1))
Imports growth = f (EXPORT(t-2))
Exports growth = f (GDP(t-1))
Table 8 Causality Relationship between Exports, Imports and GDP in Laos
Variables
EXPORT IMPORT GDP
Coefficient t-stat Coefficient t-stat Coefficient t-stat
Constant 31.461*** 3.588 15.906** 2.422 1.653 0.319
EXPORT(t-1) -0.223 -1.288 0.450** 1.649 0.947*** 3.391
IMPORT(t-1) 0.006 0.044 0.019 0.092 0.205 0.981
GDP(t-1) 0.194** 1.898 -0.057 -0.351 0.453*** 2.740
Log-Likelihood 880.028
AIC 917.860
BIC -413.014
Source: Computation
Notes: ** and *** denote 5% and 1% levels of significance respectively.
46 Chapter 3 W. Chinnakum and S. Sriboonchitta
Next, we provide the KS Test for if the probability transforms are uniform(0,1)
and the null hypothesis of KS Test is variable has uniform distribution and the result
from Table 9 rejects the null hypothesis for all 3 margins which implied that GDP
growth, exports growth and imports growth ,in the case Laos, have uniform distribution.
We also employ the Ljung–Box tests on the standardized residuals in levels reported in
Table 9 and the result highlights no autocorrelation. These results provide significant
evidence that our marginal models are correctly specified and hence copula model will
not be mispecified.
Table 9 testing the assumptions of i.i.d and Test for Autocorrelation
KS test for uniform distribution
Null Hypothesis: Variable has uniform distribution
statistic pValue Hypothesis
Margins of GDP growth 0.112 0.826 0 (acceptance)
Margins of exports growth 0.082 0.984 0 (acceptance)
Margins of imports growth 0.094 0.945 0 (acceptance)
Box-Ljung Test for Autocorrelation
Null Hypothesis: No autocorrelation
Q-Stat pValue Hypothesis
Margins of GDP growth 0.729 15.803 0 (acceptance)
Margins of exports growth 0.717 15.990 0 (acceptance)
Margins of imports growth 0.963 10.292 0 (acceptance)
Source: Computation
Table 10 Copula correlation matrix Family Copula parameter Kendall’s tau
GDP and Export Clayton 0.141 0.066
GDP and Import Independence 0.000 0.000
Export and Import
condition on GDP Frank 9.021 0.637
Source: Computation
Table 10 shows that, in the case of GDP-export pair is given to the Clayton
copula and the Export-Import pair is given to the Frank copula while there is no relation
between GDP and Import which support our VAR model. Moreover, the Kendall’s tau
of GDP-export pair and Export-Import pair are positive indicate positive dependence of
each pair.
3) Long-run relationship among exports, imports and GDP via copula-VAR model
for Philippines
In the case of the Philippines, the result indicates that exports and imports led
economic growth. Table 11 shows that the elasticity of IMPORT(t-5) is greater than the
elasticity of other variables that and a 1% increase in IMPORT(t-5) leads to a gain in
GDP growth of 2.575%.
Asian Economic Reconstruction and Development under New Challenges 47
Table 11 Causality Relationship between Exports, Imports and GDP in the
Philippines
Variables EXPORT IMPORT GDP
Coefficient t-stat Coefficient t-stat Coefficient t-stat
Constant 5.681** 2.249 2.972 1.096 4.009* 1.915
EXPORT(t-1) -0.035 -0.149 0.698*** 2.687 -0.616** -2.184
IMPORT(t-1) 0.087 0.343 0.224 0.802 0.826*** 2.728
GDP(t-1) 0.323* 1.655 -0.367* -1.707 0.791*** 3.382
EXPORT(t-2) -0.583** -2.012 0.579* 1.859 -0.498 -1.405
IMPORT(t-2) -1.230*** -3.954 1.458*** 4.365 -1.030*** -2.708
GDP(t-2) -0.769*** -3.202 0.859*** 3.328 -0.232 -0.791
EXPORT(t-3) -0.571* -1.842 0.496* 1.626 0.163 0.425
IMPORT(t-3) -0.477 -1.432 0.268 0.819 -0.694* -1.681
GDP(t-3) -0.121 -0.469 -0.039 -0.156 -0.422 -1.324
EXPORT(t-4) 0.419* 1.942 -0.360 -1.441 -0.057 -0.149
IMPORT(t-4) 0.650*** 2.804 -0.508* -1.896 -0.241 -0.583
GDP(t-4) 0.362** 2.022 -0.438** -2.114 0.089 0.278
EXPORT(t-5) -0.218 -0.990 -0.624** -2.399 1.823*** 4.269
IMPORT(t-5) -0.318 -1.346 -0.740*** -2.653 2.575*** 5.618
GDP(t-5) -0.407** -2.230 0.309 1.433 0.580 1.640
EXPORT(t-6) -0.242 -1.131 0.408 1.486 0.557 1.029
IMPORT(t-6) 0.195 0.848 -0.153 -0.518 1.218** 2.100
GDP(t-6) 0.154 0.865 -0.123 -0.541 0.146 0.325
Log-Likelihood -285.905
AIC 625.810
BIC 663.643
Source: Computation
Notes: *,** and *** denote 10%, 5% and 1% levels of significance respectively.
For imports growth equation (second column), Table 11 shows exports growth,
GDP growth and its own lag are important factors to determine imports growth. The
results indicate that the elasticity of IMPORT(t-2) is greater than the elasticity of other
variables; and that a 1% increase in IMPORT(t-2) leads to a gain in imports growth of
1.458%. The exports growth is also determined by imports, GDP and its past values.
The result indicates that the elasticity of IMPORT(t-2) is greater than the elasticity of
other variables; and that a 1% increase in IMPORT(t-2) increases exports growth by
1.230%. Therefore, our result supports the ELG, GLE and ILG in Philippines.
From Table 11 above, we can write this relation in the functional form as follow:
GDP growth = f(EXPORT(t-1), IMPORT(t-1), GDP(t-1),
IMPORT(t-2), IMPORT(t-3), EXPORT(t-5),
IMPORT(t-5), IMPORT(t-6))
48 Chapter 3 W. Chinnakum and S. Sriboonchitta
Imports growth = f (EXPORT(t-1), GDP(t-1), EXPORT(t-2),
IMPORT(t-2), GDP(t-2), EXPORT(t-3), IMPORT(t-4),
GDP(t-4), EXPORT(t-5), IMPORT(t-5))
Exports growth = f(GDP(t-1), EXPORT(t-2), IMPORT(t-2),
GDP(t-2),EXPORT(t-3),EXPORT(t-4),
IMPORT(t-4), GDP(t-4), GDP(t-5))
Next, we provide the KS Test for whether the probability transforms are
uniform(0,1) and the null hypothesis of KS Test is variable has uniform distribution.
The result rejects the null hypothesis for all 3 margins which implied that GDP growth,
exports growth and imports growth, in the case Philippines, have uniform distribution.
We also employ the Ljung–Box tests on the standardized residuals in levels reported in
Table 12 and the result highlights no autocorrelation. These results provide significant
evidence that our marginal models are correctly specified and hence copula model will
not be mis-specified.
Table 13 shows the optimal copulas and their estimated parameters. The
Gaussian copula is appropriate family to capture the dependence structure of GDP-
export pair and GDP-Import pair while Export-Import pair is given to the Clayton
copula. Moreover, the Kendall’s taus of all pairs are positive represent that the ranks of
both variables in each pair increase together.
Table 12 Testing the assumptions of i.i.d and Test for Autocorrelation
KS test for uniform distribution
Null Hypothesis: Variable has uniform distribution
statistic pValue Hypothesis
Margins of GDP growth 0.1343 0.6198 0 (acceptance)
Margins of exports growth 0.0642 0.9995 0 (acceptance)
Margins of imports growth 0.0826 0.9825 0 (acceptance)
Box-Ljung Test for Autocorrelation
Null Hypothesis: No autocorrelation
Q-Stat pValue Hypothesis
Margins of GDP growth 11.9896 0.9164 0 (acceptance)
Margins of exports growth 22.4147 0.3184 0 (acceptance)
Margins of imports growth 13.6220 0.8491 0 (acceptance)
Source: Computation
Asian Economic Reconstruction and Development under New Challenges 49
Table 13 Copula correlation matrix
Family Copula parameter Kendall’s tau
GDP and Export Gaussian copula 0.607 0.39
GDP and Import Gaussian copula 0.780 0.54
Export and Import
condition on GDP Clayton copula 1.176 0.39
Source: Computation
4) Long-run relationship among exports, imports and GDP via copula-VAR model
for Singapore
In the case of Singapore, the result indicates that exports and imports led
economic growth. In contrast, GDP does determine neither imports nor exports. This
result implies that ELG and ILG but not GLE in Singapore and highlights imports on
GDP growth and exports policy to encourage economic growth.
Moreover, Table 14 shows that the elasticity of imports is greater than the
elasticity of the exports and a 1% increase in imports leads to a gain in GDP growth of
1.941% at 5 percent significant level. We can write this relation in the functional form
as follow:
GDP growth = f(EXPORT(t-2), IMPORT(t-2), GDP(t-2),
EXPORT(t-6), IMPORT(t-6), GDP(t-6))
Imports growth = f (EXPORT(t-5), IMPORT(t-5))
Exports growth = f (EXPORT(t-1), IMPORT(t-1))
Table 14 Causality Relationship between Exports, Imports and GDP in Singapore
Variables EXPORT IMPORT GDP
Coefficient t-stat Coefficient t-stat Coefficient t-stat
Constant 4.087 0.653 4.312 0.651 7.694* 1.667
EXPORT(t-1) 1.273* 1.879 -1.689 -1.517 1.321 1.361
IMPORT(t-1) 1.247* 1.740 -1.758 -1.493 1.387 1.351
GDP(t-1) 0.179 0.359 -0.238 -0.290 0.590 0.824
EXPORT(t-2) 0.390 0.356 0.009 0.006 1.354* 1.690
IMPORT(t-2) 0.262 0.226 0.568 0.377 1.941** 2.291
GDP(t-2) -0.295 -0.365 1.068 1.017 -1.245** -2.108
EXPORT(t-3) 0.061 0.072 -0.329 -0.262 0.518 0.625
IMPORT(t-3) 0.196 0.220 0.074 0.056 -0.180 -0.206
GDP(t-3) -0.626 -1.005 0.577 0.624 0.234 0.383
EXPORT(t-4) 1.189 0.925 -1.310 -1.331 0.462 0.351
50 Chapter 3 W. Chinnakum and S. Sriboonchitta
Variables EXPORT IMPORT GDP
Coefficient t-stat Coefficient t-stat Coefficient t-stat
IMPORT(t-4) 0.595 0.438 -1.317 -1.265 1.361 0.980
GDP(t-4) 0.223 0.235 -0.616 -0.848 0.803 0.829
EXPORT(t-5) 0.594 0.878 -1.419* -1.724 0.608 0.730
IMPORT(t-5) 0.953 1.332 -1.596* -1.834 0.862 0.978
GDP(t-5) 0.123 0.247 -0.940 -1.549 0.958 1.560
EXPORT(t-6) 1.170 1.411 -0.059 -0.096 -1.273* -1.759
IMPORT(t-6) 1.377 1.571 -0.456 -0.698 -1.586** -2.072
GDP(t-6) 0.860 1.406 -0.282 -0.618 -1.181** -2.212
Log-Likelihood -243.356
AIC 540.712
BIC 578.544
Source: Computation
Notes: *,** and *** denote 10%, 5% and 1% levels of significance respectively.
Table 15 presents the KS Test for if the probability transforms are uniform(0,1)
and the null hypothesis of KS Test is variable has uniform distribution and the result
from Table 15 rejects the null hypothesis for all 3 margins which implied that GDP
growth, exports growth and imports growth ,in the case Singapore, have uniform
distribution. We also employ the Ljung–Box tests on the standardized residuals in levels
reported in Table 15 and the result highlights no autocorrelation. These results provide
significant evidence that our marginal models are correctly specified.
Table 15 Testing the assumptions of i.i.d and Test for Autocorrelation
KS test for uniform distribution
Null Hypothesis: Variable has uniform distribution
statistic pValue Hypothesis
Margins of GDP growth 0.1343 0.6198 0 (acceptance)
Margins of exports growth 0.0642 0.9995 0 (acceptance)
Margins of imports growth 0.0826 0.9825 0 (acceptance)
Box-Ljung Test for Autocorrelation
Null Hypothesis: No autocorrelation
Q-Stat pValue Hypothesis
Margins of GDP growth 11.9896 0.9164 0 (acceptance)
Margins of exports growth 22.4147 0.3184 0 (acceptance)
Margins of imports growth 13.6220 0.8491 0 (acceptance)
Source: Computation
Asian Economic Reconstruction and Development under New Challenges 51
Next we estimate the copula correlation and from the AIC and BIC perspective,
the Rotated Gumbel copula was the best among parameter copula to capture the
dependence structure of EXPORT –GDP pair, IMPORT- GDP pair and EXPORT –
IMPORT pair (Table 16). Moreover, the Kendall’s taus of all pairs are positive
suggests that the ranks of both variables in each pair increase together.
Table 16 Copula correlation matrix
Family Copula
parameter
Kendall’s tau
GDP and Export rotated Gumbel copula (180 degrees;
“survival Gumbel”) 3.124 0.68
GDP and Import rotated Gumbel copula (180 degrees;
“survival Gumbel”) 5.283 0.81
Export and Import
condition on GDP
rotated Gumbel copula (180 degrees;
“survival Gumbel”) 3.336 0.7
Source: Computation
5) Long-run relationship among exports, imports and GDP via copula-VAR model
for Vietnam
The result of Table 17 indicates that exports and imports are important factors to
determined GDP growth in Vietnam. Moreover, there is bidirectional relation between
imports and GDP which support ILG. In contrast, there is no evidence suggests the
causal direction from GDP to exports. The result also shows that exports led imports
and imports led exports in Vietnam. We can write this relation in the functional form as
follow:
GDP growth = f(IMPORT(t-1),EXPORT(t-2),IMPORT(t-2), EXPORT(t-3),
IMPORT(t-3),GDP(t-3), EXPORT(t-4), GDP(t-4) ,
EXPORT(t-6), IMPORT(t-6))
Imports growth = f (EXPORT(t-2), IMPORT(t-2), GDP(t-5) ,EXPORT(t-6))
Exports growth = f (EXPORT(t-2), EXPORT(t-3), IMPORT(t-3), IMPORT(t-6))
52 Chapter 3 W. Chinnakum and S. Sriboonchitta
Table 17 Causality Relationship between Exports, Imports and GDP in Vietnam
Variables
EXPORT IMPORT GDP
Coefficient t-stat Coefficient t-stat Coefficient t-stat
Constant 14.389** 2.189 4.728 0.563 17.589** 2.068
EXPORT(t-1) 0.505 1.554 -0.483 -1.565 0.050 0.281
IMPORT(t-1) 0.469 1.131 -0.558 -1.417 0.657*** 2.894
GDP(t-1) 0.247 0.588 0.132 0.332 -0.105 -0.456
EXPORT(t-2) 0.814** 2.485 -0.918*** -2.963 0.391* 1.648
IMPORT(t-2) 0.682 1.631 -1.035*** -2.614 0.794*** 2.620
GDP(t-2) 0.295 0.695 -0.003 -0.007 -0.183 -0.597
EXPORT(t-3) 0.889*** 3.331 -0.378 -1.313 1.044*** 4.027
IMPORT(t-3) 1.176*** 3.450 -0.551 -1.496 1.421*** 4.293
GDP(t-3) -0.043 -0.124 -0.597 -1.603 -0.793** -2.366
EXPORT(t-4) -0.245 -0.995 -0.187 -0.621 -0.627** -2.069
IMPORT(t-4) -0.169 -0.537 -0.627 -1.626 -0.452 -1.168
GDP(t-4) 0.393 1.233 0.227 0.582 0.879** 2.244
EXPORT(t-5) 0.270 1.090 0.105 0.345 0.524 1.458
IMPORT(t-5) -0.030 -0.094 0.387 0.998 0.190 0.413
GDP(t-5) -0.188 -0.585 -0.679* -1.728 -0.565 -1.216
EXPORT(t-6) -0.225 -1.126 -0.482* -1.692 -0.468** -1.791
IMPORT(t-6) -0.449* -1.758 0.087 0.240 -0.563** -1.688
GDP(t-6) 0.289 1.116 -0.214 -0.582 0.194 0.573
Log-Likelihood -354.725
AIC 763.451
BIC 801.283
Source: Computation
Notes: *,** and *** denote 10%, 5% and 1% levels of significance respectively.
Table 18 presents the KS Test for if the probability transforms are uniform(0,1)
and the null hypothesis of KS Test is variable has uniform distribution and the result
from Table 18 rejects the null hypothesis for all 3 margins which implied that GDP
growth, exports growth and imports growth ,in the case Vietnam, have uniform
distribution. We also employ the Ljung–Box tests on the standardized residuals in levels
reported in Table 18 and the result highlights no autocorrelation. These results provide
significant evidence that our marginal models are correctly specified.
Asian Economic Reconstruction and Development under New Challenges 53
Table 18 Testing the assumptions of i.i.d and Test for Autocorrelation
KS test for uniform distribution
Null Hypothesis: Variable has uniform distribution
statistic pValue Hypothesis
Margins of GDP growth 0.0946 0.9404 0 (acceptance)
Margins of exports growth 0.0757 0.9936 0 (acceptance)
Margins of imports growth 0.0950 0.9384 0 (acceptance)
Box-Ljung Test for Autocorrelation
Null Hypothesis: No autocorrelation
Q-Stat pValue Hypothesis
Margins of GDP growth 9.6459 0.9741 0 (acceptance)
Margins of exports growth 17.5550 0.6167 0 (acceptance)
Margins of imports growth 9.5472 0.9757 0 (acceptance)
Source: Computation
Next we estimate the copula correlation and from the AIC and BIC perspective,
the Frank copula was the best among parameter copula to capture the dependence
structure of EXPORT-GDP and IMPORT-GDP while the Gumbel copula was the best
among parameter copula to capture the dependence structure of EXPORT- IMPORT
(Table 19).
Table 19 Copula correlation matrix
Family Copula parameter Kendall’s tau
GDP and Export Frank Copula 3.767 0.37
GDP and Import Frank Copula 4.977 0.46
Export and Import
condition on GDP Gumbel Copula 3.232 0.69
Source: Computation
4.3 Impulse response function
Next, we will present impulse response function (IRFs) which is tool to analyze
dynamic effects of the system when the model received the impulse. IRFs could provide
more insight into how shocks to exports and imports affect economic growth (and vice
versa). Figure 2-6 provide results for the IRFs for Indonesia, Laos, Philippines,
Singapore and Vietnam, respectively.
Figure 2 the Impulse Response Analysis for Indonesia
54 Chapter 3 W. Chinnakum and S. Sriboonchitta
According to Figure 2, the first panel shows the impulse response of GDP
growth to exports growth and imports growth for Indonesia. The IRFs shows the
response of GDP to shock on exports and the response of GDP on imports are positive
in the second to seventh period and then the effect gets weaker and become zero after
eight years.
In order to check for reverse causality from GDP to exports and imports the
responses of exports and imports are reported. When the impulse is GDP growth, the
response of exports growth rate is positive and decrease to zero line after ten years.
However, the response of imports growth to GDP shock is insignificantly different from
zero.
Finally, the IRFs shows the response of imports to shock of exports is negative
in the first and second year and then become a positive after four years and the effect
gets weaker after seven years. In contrast, the response of exports to imports is small
negative (around 0-4%) and become zero after eight years.
This finding reinforces the result from VAR analysis which provided support for
the ELG and ILG argument.
Figure 3 the Impulse Response Analysis for Laos
Figure 3 presents the results from IRFs analysis for Laos. First, there is no
evidence in support of ILG as the response of GDP growth due to shocks of imports
growth is not significantly different from zero at all horizons. However, IRFs supports
ELG as a shock of exports has a positive and significant effect on output growth. Figure
3 also shows output growth has a negative impact on exports while there is positive
impact of GDP on imports and the response of exports and imports become fluctuate
around zero line after three years. Finally, there is no evidence appear to confirm
relationship between imports and exports
Therefore, it supports our VAR findings that exports growth causes GDP and
further highlights the significant role of exports in Laos’s economic growth.
Asian Economic Reconstruction and Development under New Challenges 55
Figure 4 the Impulse Response Analysis for Philippines
According to the Figure 4, first panel presents the impact of GDP growth (GDP)
shock, exports growth (EXPORT) shock and imports growth (IMPORT) shock on GDP.
Response of GDP to IMPORT obvious fluctuation whiles the response of GDP to
EXPORT smooth fluctuation and reach to initial equilibrium. The result also shows that
the imports growth (IMPORT) has large effect on GDP growth than exports growth
(EXPORT).
The second panel of Figure 4 shows the impact of GDP growth (GDP) shock,
exports growth (EXPORT) shock and imports growth (IMPORT) shock on exports
growth. Response of EXPORT to IMPORT and GDP obvious fluctuation and the affect
move out from initial equilibrium in the long-run. The result suggests that the IMPORT
has large effect on exports growth than effect of GDP on EXPORT.
The third panel presents the impact of GDP growth (GDP) shock, exports
growth (EXPORT) shock and imports growth (IMPORT) shock on imports growth.
Response of IMPORT to GDP and the response of IMPORT to EXPORT obvious
fluctuation around the zero line and the impact of imports itself have large effect than
GDP growth and exports growth.
Thus, IRFs suggests imports in Philippines have large effect on other variables
than exports growth and GDP growth which highlight important of imports policy to
driving economic growth.
To investigate further the impact of exports growth on GDP growth as compared
to imports growth, we then have used impulse response function to trace the time paths
of GDP in response to a one-unit shock to the variables such as exports growth and
imports growth. The first panel of Figure 5 shows the response of GDP to shock of
exports obvious fluctuation. The effect is negative and the response reach minimum
when the period of response is 4, then the response extent increase. The response of
GDP to shock of imports also fluctuation but the imports growth has less effect than
exports growth.
56 Chapter 3 W. Chinnakum and S. Sriboonchitta
Figure 5 the Impulse Response Analysis for Singapore
The second panel of Figure 5 shows the response of exports growth to shock of
GDP and imports growth which obvious fluctuate. Moreover, the response of exports
growth to shock of GDP has larger effect than imports growth.
Finally, Figure 5 shows the response of imports to shock of GDP and exports
which varies all time horizons. Moreover, the response of imports growth to shock of
exports has larger effect than GDP growth.
Figure 6 the Impulse Response Analysis for Vietnam
According to the Figure 6, the first panel shows the impact of GDP growth
(GDP) shock, exports growth (EXPORT) shock and imports growth (IMPORT) shock
on GDP. The response of GDP to one S.D. innovations of imports growth is negative
from the first period, then the response reach minimum when the period of response is
4, after that, the response extent increases and reaches to initial equilibrium after ten
years. The response of GDP to exports growth fluctuates around zero line and reaches to
initial equilibrium after ten years. The result shows that the imports growth has large
effect on GDP growth than exports growth.
The second panel of Figure 6 shows the impact of GDP growth (GDP) shock,
exports growth (EXPORT) shock and imports growth (IMPORT) shock on exports
Asian Economic Reconstruction and Development under New Challenges 57
growth. Response of EXPORT to GDP is negative and the response extent increases
when the period of response is 7. The response of EXPORT to IMPORT obvious
fluctuates but moves around zero line. The result shows that the imports growth
(IMPORT) has large effect on exports growth than GDP growth (GDP).
Finally, Figure 6 shows the impact of shock GDP growth (GDP), exports growth
(EXPORT) and imports growth (IMPORT) on IMPORT. Response of IMPORT to GDP
and the response of IMPORT to EXPORT obvious fluctuate and move in the same
direction.
5. Concluding remarks
In this study, Copula-VAR analysis was applied to investigate the causal
relationship among the variables of annual GDP growth, import growth, and export
growth belonging to the period 1980–2010 of ASEAN countries (Brunei, Vietnam,
Malaysia, Indonesia, The Philippines, Singapore, Thailand, and Laos). The
contributions of this paper are the following: 1) export growth and import growth are
included in the model as endogenous variables which previous empirical studies specify
as exogenous variables. 2) We employ copula-VAR model (suggested by Bianchi, et. al
(2010)) and the result suggests that the copula approach are fit to construct the VAR
model in ASEAN case.
In particular, these results indicate that relationship among imports, exports, and
output have different qualitative relationships in each country. Moreover, results suggest
there is a causal relation among imports, exports, and output in Malaysia, Thailand, and
Brunei. In contrast, the study found empirical evidence in support of bi-directional
causal relationship between exports and GDP growth for Laos and The Philippines.
Furthermore, the results of Indonesia, Singapore, and Vietnam support only ELG
hypothesis, not GLE hypothesis. Empirical results also suggest that there is evidence in
support of ILG hypothesis for The Philippines, Indonesia, Singapore, and Vietnam.
This study’s results confirm that the exclusion of imports and the singular focus of
many past studies on merely the role of exports as the engine of growth may be
misleading or lead to incomplete results. Current empirical evidence from selected
ASEAN countries provides empirical support for both ELG and ILG hypothesis, and in
some cases there is also evidence to suggest the impact of import growth as larger than
export growth on GDP growth, which implies the importance of import policy. Thus, it
is reasonable to conclude that for several ASEAN countries, both exports and imports
play a very important role in stimulating economic growth.
58 Chapter 3 W. Chinnakum and S. Sriboonchitta
ACKNOWLEDGMENT
This work was granted by office of the Higher Education Commission of Thailand. The first
author was supported by a CHE PhD scholarship.
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60 Chapter 3 W. Chinnakum and S. Sriboonchitta